Embodiments of the present invention generally relate to fluorometric sensors and fluorometers for determining and monitoring the concentration of one or more substances in a liquid sample, and more particularly to the calibration of such fluorometric sensors and fluorometers.
In cleaning and antimicrobial operations, commercial users (e.g., restaurants, hotels, food and beverage plants, grocery stores, etc.) rely upon the concentration of the cleaning or antimicrobial product to make the product work effectively. Failure of a cleaning or antimicrobial product to work effectively (due to concentration issues) can cause a commercial user to perceive the product as lower quality. End consumers may also perceive the commercial user as providing inferior services. In addition, commercial users may be investigated and/or sanctioned by government regulatory and health agencies. Accordingly, there is a need for a system that can determine if the concentration of a product is within a specified concentration range. The same may be true for other applications, such as water care, pest control, beverage and bottling operations, packaging operations, and the like.
One method of monitoring the concentration of a product relies on monitoring the fluorescence of the product that occurs when the sample (and the product within the sample) is exposed to a predetermined wavelength of light. For example, compounds within the product or a fluorescent tracer added to the product may fluoresce when exposed to certain wavelengths of light. The concentration of the product can then be determined using a fluorometer that measures the fluorescence of the compounds and calculates the concentration of the chemical based on the measured fluorescence.
Fluorometric spectroscopy concerns the detection of fluorescent light emitted by a sample of interest. It involves using a beam of light, usually ultraviolet (UV) light, that excites the electrons in molecules of certain compounds in the sample and causes them to emit light of a lower energy (i.e., to “fluoresce”). There are several types of fluorometers for measuring emitted fluorescence. Fluorometers generally have of a source of excitation radiant energy, an excitation wavelength selector, a sample cell to contain the sample material, an emission wavelength selector, a detector with signal processor and a readout device. Filter fluorometers use optical filters to isolate the incident light and fluorescent light. Spectrofluorometers use diffraction grating monochromators to isolate the incident light and fluorescent light.
The accuracy of a fluorometer's measurements, and ultimately the accuracy of the calculated concentrations, depend upon the fluorometer's ability to account for various factors in the field. Accordingly, many fluorometers are calibrated prior to measuring fluorescence in order to correct for water properties such as background fluorescence that can significantly affect fluorescence measurements if not taken into account. In addition, water properties often vary over time and across sites, leading to further difficulty in obtaining accurate fluorescence measurements in the field.